Two-phase permanent antifreeze fluid



United States Patent O TWO-PHASE PERMANENT ANTIFREEZE FLUID Theodore C. Heisig, White Plains, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application January 13, 1950, Serial No. 138,513

9 Claims. (Cl. 252-75) This invention relates to polyhydric alcohol anti-freeze liquids of the types adapted to be added to water or an equivalent liquid in the circulating cooling system of an internal combustion engine or like device.

The invention is applicable to the various types of water-miscible polyhydric alcohols employed as freezing point depressants for water and equivalent liquids in circulating cooling systems. Such alcohols include ethylene and other glycols, polyglycols and glycerine. The preferred embodiment of the present invention employs ethylene glycol as the freezing point depressant.

in service, such anti-freeze liquids give riseto serious corrosion of the metals such as steel, brass, copper, aluminum, solder, and their alloys which they contact in circulating systems. Various corrosion inhibitors and inhibitor combinations have been employed in an effort to overcome that difficulty. A number of such inhibitors and combinations thereof that have proven successful are disclosed in the copending application of William R. Smith, Serial Number 63,629 filed December 4, 1948, and entitled Anti-Freeze Liquids, now Patent No. 2,524,484 dated October 3, 1950.

A further difficulty encountered in the use of such anti-freeze liquids is foaming. In practice, it has been found that the water and anti-freeze mixtures foam at times to an extent to escape from the cooling system and seriously reduce the quantity of cooling fluid remaining in the system so that the engine or other device being cooled may become seriously overheated. While this foaming to a limited extent may be traced to the use of certain corrosion inhibitors,the principal causes appear to be the mechanical design or plumbing of the cooling systems, the use of certain proprietary compounds in an effort to inhibit corrosion, the retention of small amounts of cleaning compounds in the cooling systems because of improper flushing, the circulating means in the cooling system, the radical changes in temperature of the cooling fluid, the trapping of air in heaters, etc., during periods of inactivity, and the leakage of air or other gases into the system.

Typical anti-foam mixtures or agents, such as are used in boilers and like places where mixtures of water and various chemical compounds are found to foam excessively, have been tried in such cooling liquids and found unsuccessful. Other types of anti-foam agents have been tried and found difiicult to dissolve or disperse or to stay in such dissolved or dispersed phases during use. The latter is a particularly difiicult problem with internal combustion engines such as are used in automobiles wherein there may be long periods of inactivity between periods of use.

Anti-foam mixtures or agents known to date have been characterized by a specific gravity less than that of the resultant anti-freeze mixture in the engine and characterized by a tendency to separate from the antifreeze mixture on standing. Hence, they are objectionable in that on standing they tend to collect in the upper neck of the radiator and become susceptible to discharge through the overflow pipe when the engine is first started and the mixture is expanding. Loss may also occur when the radiator is overfilled.

It is an object of this invention to provide a novel antifreeze liquid wherein foaming is inhibited to an extent to substantially eliminate the foam problem despite any foam developing circumstances that may be encountered.

A further object of the invention is the provision of a novel anti-freeze liquid of the so-called permanent type 2,693,451 Patented Nov. 2, 1954 wherein foaming is inhibited over long periods of service without the addition of more foam inhibiting agent.

Still another object of the invention is the provision of a novel method of combining an anti-freeze liquid with an anti-foam agent wherein the latter is placed in and remains in the resultant coolant in an operative phase for substantially the entire effective life of the antifreeze.

Still a further object of the invention is the provision of a novel anti-freeze liquid of the permanent type wherein the anti-foam agent contained therein is of a specific gravity substantially equal to or slightly above the specific gravity of the final mixture.

Other objects and advantages of the invention will appear from the following description taken in connection with the appended claims.

In brief, the present invention is directed to an antifreeze liquid having a water-miscible polyhydric alcohol base and an agent capable of inhibiting foam in the final coolant in which the anti-freeze liquid is incorporated. More specifically, the invention is concerned with an anti-freeze liquid incorporating a corrosion inhibitor or combinations thereof and an anti-foam agent of the type including an organo-silicon compound, preferably of the silicone type, the agent having a specific gravity substantially equal to or slightly greater than the specific gravity of the anti-freeze mix in the engine and present in sufficient amount and in phase such that it will inhibit foaming of the resultant mixture of the liquid with the water customarily used in a coolant system.

The water miscible polyhydric alcohol, employed as a base for the anti-freeze liquid, includes such alcohols as ethylene and other glycols, polyglycols and glycerine.

Typical anti-foam agents include condensation products of organo-silicone oxides such as those condensation products containing a plurality of silicon atoms linked through oxygen atoms, each silicon atom having attached thereto at least one organic radical. Such compounds have come to be called silicones by reason of their containing the so-called silicone radicals, i. e.

Such compounds may be formed by polymerization or condensation of organic silicols, the latter including mono-, di-, and tri-silicols as well as mixtures thereof.

Such compounds may be represented by the following formula:

in which n is one or more and R represents similar or dissimilar radicals such as alkyl, aryl, aralkyl, alkaryl or heterocyclic groups or the terminal Rs may be substituted by hydroxyl groups, or all but one of the Rs attached to the silicon atom may be substituted by hydroxyl groups or halides.

Such condensation products may be formed as straight chains, cyclic or cross polymerization products and may be liquids or solids.

Preferably R is a single organic radical of low molecular weight such as methyl, ethyl and short chain alkyl groups. Compounds having organic radicals of high mo lecular weight such as phenyls or compounds containing organic radicals of both high and low molecular weights, can be used.

A preferred compound is di-methyl silicone having the following formula:

CH3 CH3 CH3- iO i-CH3 Ha is OH:

in which n is one or more. In most cases, it is believed that the product contains a number of such polymers of different chain lengths and perhaps different chain types.

Such compounds are available in a wide range of viscosities, a viscosity in the range of 50 cs. (centistokes) to 1000 cs., and preferably a viscosity in the range of approximately 100 cs. to 500 cs., being preferred.

Another class of organo-silicon oxide condensation products contemplated in practicing the invention are the organo-silicate condensation products represented by the following formula:

in which n is one or more and R likewise represents similar or dissimilar organic radicals such as alkyl, aryl, aralkyl, alkaryl or heterocyclic groups. Such compounds may be prepared by controlled or partially hydrolysis of the tetraorthosilicate esters with water. Again, organic radicals of low molecular weight such as methyl and ethyl are preferred although it is contemplated that radicals of higher molecular Weights can be used alone or in combination with radicals of low molecular weight.

As the foregoing compounds and their methods of preparation are well known to the art and no claim thereto is made herein, further discussion thereof is considered unnecessary.

A preferred organo-silicon compound is a dirnethyl silicone linear polymer chain-stopped with methyl groups and having a viscosity of about 250 centistokes, the silicone being mixed with about 5% very finely divided siliceous material such as finely divided silica. A suspension is formed which is relatively inert in contact with known metals and plastics and is relatively non-inflammable. If desired, the siliceous material may be omitted.

Still another preferred organo-silicon compound is methylphenyl silicone of a viscosity of about 500 centistoke(s3 at 250 C., and a specific gravity of about 1.11 at 25 The preferred anti-foam agents not only include an organo-silicon compound but also a liquid hydrocarbon which has a specific gravity and is present in such amount that the specific gravity of the final anti-foam mix used is substantially equal to or slightly in excess of the specific gravity of the final coolant, i. e., the alcohol and water mix, used in the engine. Preferably, the amount of liquid hydrocarbon used is such that when the antifoam mix is mixed with the alcohol alone, having a specific gravity of about 1.116 to 1.119, the anti-foam mix or a major part thereof floats on the surface of the alcohol. This is desirable to insure that none of the antifoam mix is left in the anti-freeze container when the latter is emptied. Liquid hydrocarbons available for this purpose include light and heavy cycle fuel oils, furfural extracts and light fractions from residues from deasphalting. Hydrocarbons weighted by halogenation such as a chlorinated bi-phenyl sold by the Monsanto Chemical Company under the trade name Arochlor 1248 may be used. If the heavy hydrocarbon be too heavy initially: sufficient of a lighter liquid hydrocarbon having a specific gravity of less than 1.00 can be added to bring the specific gravity of the anti-foam mix down to the desired range. All the above combinations have been found desirable to enable a homogeneous dispersion of the silicone compound in the final coolant. For instance, a silicone containing siliceous material, if used by itself, tends to agglomerate in the anti-freeze and remain as a single mass. With the combinations described above, there is no such agglomeration.

A preferred heavy hydrocarbon is chlorinated biphenyl which has a specific gravity at 77 F. of 1.447 to 1.457, a boiling range of 340 to 370 C., a flash COC F. of 379384, a pour F. of 19.4, a refractive index of 1.630-1.63l at 20 C., a viscosity at 100 F. (SU) of 185240; at 130, 6978 and at 210 F., 36-37. It weighs about 12.1 lbs./ gal. The compound is nonoxidising, non-volatile, non-corrosive to metals and is not hydrolyzed by water, alkalies or acids.

The lighter hydrocarbon preferably used, if required to reduce the Specific gravity of the anti-foam mix, is of a naphthenic type with a specific gravity of less than 1. Depending on the actual specific gravities of the lighter oil and the heavy hydrocarbon, the proportions thereof will vary.

The preferred inhibitor combination, as disclosed in the aforesaid Smith application, includes an alkali metal phosphate, an alkali metal silicate and mercaptobenzothizole or an alkali metal salt of mercaptobenzothiazole, the latter being preferred over mercaptobenzothiazole. While the various alkali metal salts including those of sodium, potassium, lithium, etc., may be used, the sodium salt is preferred from the standpoint of availability and effectiveness. Where the sodium salt is referred hereinafter, it is to be understood that the corresponding salts of the other alkali metals may be substituted therefor.

The sodium phosphate employed is the trisodium phosphate. Ordinarily the trisodium phosphate dodecahydrate (Na3PO4.12H2O) is used. The sodium silicate, which is conveniently employed in the form of a concentrated aqueous solution, is preferably one having a high SiOz to NaOz mol ratio in excess of 2.5:1, such as the well-known N brand of sodium silicate manufactured by the Philadelphia Quartz Company having a SiOz to NaOz mol ratio of about 3.2: 1. The mercaptobenzothiazole can be used in the form of a powder and dissolved in the glycol anti-freeze. The sodium mercaptobenzothiazole is preferably employed in the form of a concentrated aqueous solution of about 4550% concentration, a commercial form of the material on the market being an aqueous solution containing about 46-47% by weight of the compound.

Based on laboratory and service tests, the proportions in which the various constituents of the inhibitor are employed are set forth in the following tabulation, together with a preferred example of each combination, the percentage being expressed by weight based on ethylene glycol.

Composition A Limits, Example, Percent Percent by Wt. by Wt.

Na PO4.12HzO 1. 0-3. 5 2. 38 40 B. N" Brand Sodium Silicate So1uti0n 0.8-1. 5 1.0 50% Aqueous Solution of Sodium Mercaptobenzothiazole 0. 5-1. 2 0. 68

OR EXPRESSED ON A WATER-FREE BASIS IN PERCENT BY WEIGHT BASED ON ETHYLENE GLYCOL OR EXPRESSED ON A WATER-FREE BASIS IN PERCENT BY WEIGHT BASED ON EIHYLENE GLYCOL Na3PO4 0.4-1. 6 1.03 Sodium silicate 0.3-0. 6 0. 4 Mercaptobenzothiazole 0 2-0. 5 0. 3

The anti-freeze liquid containing either of the above combinations within the limit specified in a 40% concentration in water has a pH in excess of 9 and below 12, generally about 10.711.2.

In preparing the anti-freeze liquid of Composition A above, the trisodium phosphate dodecahydrate is first dissolved at an elevated temperature of -200 F. in a small amount of water. The sodium silicate and sodium mercaptobenzothiazole solutions are mixed therewith in the order mentioned. The quantity of water employed, includ ng the'bound water of the phosphate and the free water in the silicate and mercaptobenzothiazole solutions, is preferably not substantially more than about the minimum required to maintain the said salts in solution at the elevated temperature, thus providing a nearly saturated aqueous solution at that temperature. A small flowing stream of the resultant aqueous solution, in controlled amount, 18 then admixed with a flowing stream of the alcohol c freezing point depressant, such as ethylene glycol, in controlled amount to provide about 38% by weight of the former to about 92-97% by weight of the latter inthe resultant mix. This provides an anti-freeze liquid containing roughly about 25% by weight water based on the final anti-freeze liquid, and preferably about 34% total water. Actually, the amount of water initially added to dissolve the trisodium phosphate is much less than the figure specified above for total water and represents about 1-2% by weight based on the final antifreeze liquid. The small amount of water adds materially to the ease of preparation, and to the stability of the ultimate anti-freeze liquid on storage. against sedimentation and the salt separation and yet is so small as not to affect the normal freezing point depressant prop: erties of the ultimate anti-freeze liquid as compared to substantially pure ethylene glycol or other freezing point depressant- In compounding the anti-freeze liquid of Composition B above, the procedure is essentially the same except that the mercaptobenzothiazole powder must be separately dissolved in the glycol, preferably before mixing of the streams of aqueous solution and glycol.

In using a heavy hydrocarbon having a specific gravity in a range whereby the specific gravity of the final antifoam mix is as desired, the oil may be combined with the organo-silicon compound in the following approximate proportions:

Range, Percent by Wt.

Preferred, Percent by Wt.

Silicone 10 Heavy liquid hydrocarbon 90 In using a dimethyl silicone containing siliceous material, the following provides a good anti-foam agent.

Range, Preferred, Percent Percent by Wt. by Wt.

Silicone suspension (500 cs.) Chlorinated bi-phenyl Oil (Sp. gr. of about 0.9402) Another example of a good following:

anti-foam agent is the Preferred gauge? ercen by Percent Percent by Wt. by Wt Methyl-phenyl silicone (500 cs.) Chlorinated bi-phenyl Oil (Sp. gr. of about 0.9042)" In practice, it has been found best to blend the heavy liquid hydrocarbon and the organo-silicon until uniform in appearance. If a lighter oil is required tobring the specific gravity of the final anti-foam mix within the desired limits, it is then added. The blend is then stirred vigorously to produce a uniform suspension after which it is mixed with the anti-freeze. On standing, the antifoam mix will tend to rise to the top of the container and stay on the surface of the alcohol. This is desirable to insure its transfer to the engine when the container is emptied.

The anti-foam mix is added to the anti-freeze previously prepared in an amount between 0.90 and 1.25% by volume, an amount of about 1.05% by volume being preferred.

The specific gravity of the final anti-foam mix is such that it is substantially equal to or slightly heavier than an aqueous solution containing up to 60% of the antifreeze concentrate.

It will be understood that the resulting anti-freeze liquid is ordinarily mixed with 1 times its volume of water formingv a 40% solution for use in the northern zones of most temperate climates and with about four times its volume of water to form a 20% solution for use in the southern zones of such temperate climates. However, the liquid can be mixed with water in any proportion desired to provide the required freezing point according to freezing point tables, except that the glycol anti-freeze liquid should not be employed in a higher concentration in water than about 60%, because the more concentrated liquid becomes unduly viscous at extremely low temperatures. This is typical of all glycol base anti-freeze liquids.

The resultant anti-foam mix with its relatively high specific gravity is of advantage since it has no tendency to vaporize under radiator temperatures and has a specific gravity such that in the final coolant in the engine, there is little or no tendency for the anti-foam agent to separate from the mixture in a manner such that it becomes inetfective. In the event there is separation, it will be in the nature of settling so that none of the mix is lost through the overflow pipe. This is particularly important in internal combustion engines such as are used in automobiles wherein the engines may be subject to extremely hard usage at times with long rest periods in between, and the coolant is consequently subjected to alternate periods of vigorous circulation and rest and expansion and contraction.

If a lighter oil is used in the anti-foam mix to reach the specific gravity desired, a naphthene oil is preferred because of its ability to better emulsify with a waterglycol mixture.

By reason of the substantially equal or higher specific gravity of the anti-foam mix relative to the final engine coolant, the mix tends to remain dispersed substantially homogeneously throughout the aqueous solution or to settle only slightly therein on standing. This dispersion is apparently aided by the presence of the very finely divided siliceous material. By reason of the settling of the anti-foam mix, if there is any tendency for some proportion to separate, the mix is immediately dispersed throughout the coolant as soon as the engine is started. None is lost through the overflow as might be the case if the mix were of a lower specific gravity than the coolant.

The inhibitor combinations disclosed herein have proven unusually successful, the results of tests thereof being given in detail in the above-identified Smith application to which reference is made.

The following has been found to be an especially effective anti-freeze liquid:

Percent by weight Ethylene glycol 94.6960 H2O (added) 1.4460 Na3PO4.12H2O 2.2526 Sodium silicate 0.9488 Sodium mercaptobenzothiazole 0.6466

99.9900 Dye O-Ol To the above, 1.05% by volume of anti-foam agent consisting of by weight heavy hydrocarbon and 10% by weight di-methyl silicone containing siliceous material is added.

The anti-foam agents above described, have been found to be unusually successful in inhibiting foam and in continuing such function over the life of the antifreeze. Their manner of association with the antifreeze and cooling liquid mixture is such that they are available and effective despite any long period of rest of the engine in which the coolant is used, thus making the antifreeze particularly advantageous for engines used in automotive vehicles.

The efiiciency of the anti-foaming compositions above described has been established by both laboratory tests and road tests.

In'the laboratory, with the so-called Mix-master foam tests wherein 250 cc. of 40% antifreeze solution is beaten at full speed for 60 seconds, the anti-freeze without an anti-foam agent of the above type was found to have a foam height of inch and a collapse time of 14 to 16 seconds. With the addition of 1 per cent of the anti-foam agent containing siliceous material, foam was entirely eliminated. In another case wherein water pump grease -7 was added as a contaminant, the anti-freeze without the anti-foam agent showed a foam height of 1% inches and a collapse time of 136 to 690 seconds. With the addition of about 1 per cent of the anti-foam agent containing a siliceous compound and double the amount of contaminant, the foam height was only 4; inch and the foam collapsed in 12 to 22 seconds.

In a case where 1 per cent of a proprietary corrosion inhibitor was added to the anti-freeze without anti-foam mix, a foam height of 1% inches was observed, the foam having a collapse time of 650 seconds. One per cent of the anti-foam mix eliminated all foam when as much as per cent of the proprietary compound was added to the anti-freeze. In a case where 0.2 per cent of a soluble oil was found to cause a foam height in the anti-freeze not containing anti-foam of 1% inches and a foam collapse time of over 1,000 seconds, 1 per cent of the antifoam agent was found to eliminate allfoam even when 5 times as much soluble oil was added.

To test the performance of the anti-foam agent under service conditions, high speed car tests were conducted.

These tests consisted essentially of operating a car containing the anti-freeze at abnormally high speeds continuously for a few miles and then removing the radiator cap as quickly as possible and estimating the amount of foam on the surface of the coolant. Since foaming is usually accelerated at high speeds,.this test has been decided upon as a good criterion for judging the relative foaming tendencies of anti-freeze solutions. The performance of the anti-foam mix under road conditions was excellent even with the addition of relatively large amounts of contaminants.

Obviously many modifications and variations of the invention as hereinabove set forth may be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A two-phase permanent type anti-freeze. liquid adapted to be added to Water used in cooling systems of internal combustion engines to provide a resultant coolant, said anti-freeze liquid consisting essentially of a water-miscible polyhydric alcohol freezing point depressant as the predominating constituent containing a small amount of corrosion inhibitor dissolved therein and constituting a first phase, and 0.90-1.25 by volume based on said first phase of an anti-foam mix insoluble in said polyhydric alcohol and constituting a second phase, said anti-foam mix consisting essentially of a foam inhibiting amount up to 15% by weight of a silicone having antifoam properties homogeneously dispersed in heavy hydrocarbon liquid having a specific gravity such that said anti-foam mix has a specific gravity less than that of the said first phase so that it floats on the latter, and greater than that of the coolant formed by diluting the anti-freeze liquid with water to form a coolant containing atleast 40% by volume of water so that the anti-foam mix settles in the coolant on standing.

2. A two-phase permanent type anti-freeze liquid according to claim 1, wherein the said anti-foam mix also has dispersed therein about 5% of finely divided silica based on said silicone.

3. A two-phase permanent type anti-freeze liquid according to claim 1, wherein the said hydrocarbon liquid is a mixture of a hydrocarbon oil having a specific gravity less than 1.00 with a halogenated hydrocarbon having a specific gravity greater than 1.00 and greater than that of the final anti-foam mix.

4. A two-phase permanent type anti-freeze liquid according to claim 1, wherein the anti-foam mix consists of the said silicone and about 5% of finely divided silica based on said silicone, dispersed in a mixture of chlorinated bi-phenyl and a hydrocarbon oil.

5. A two-phase permanent type anti-freeze liquid according to claim 1 wherein said polyhydric alcohol is ethylene glycol, and whereinsaid hydrocarbon liquid is a mixture of chlorinated bi-phenyl and a hydrocarbon 6. An anti-freeze liquid according to claim 5, wherein the anti-foam mix consists, by weight, 2-1'5% of silicone, 35-46% of chlorinated bi-phenyl, and 45-60% of the hydrocarbon oil.

7. A two-phase permanent type anti-freeze liquid adaptedto: be added to water used in cooling systems of internal combustion engines to provide a resultant substantially non-foaming coolant having a relatively low freezing point, consisting essentially of a water-miscible polyhydric alcohol freezing point depressant as the predominating constituent and forming a first phase, and 0.90-1.25 by volume based on said first phase of an anti-foam mix to inhibit foaming of the resultant coolant during operation of the engine forming a second phase and consisting essentially of a silicone in a foam inhibiting amount up to 15% by weight substantially homogeneously dispersed in a heavy hydrocarbon liquid having a specific gravity such that said anti-foam mix has a specific gravity greater than that of the coolant formed by diluting the anti-freeze liquid with water to provide a coolant having at least 40 per cent by volume of water so that the anti-foam mix settles in the coolant on standing.

8. A two-phase permanent type anti-freeze liquid adapted to be addedto water used in cooling systems of internal combustion engines to provide a resultant substantially non-foaming coolant having a relatively low freezing point, consisting essentially of a water-miscible polyhydric alcohol freezing point depressant as the predominating constituent and forming one phase, and 0.901.25% by weight of an anti-foam mix to inhibit foaming of the resultant coolant during operation of the engine forming a second phase and consisting essentially, by weight, 2-15% of a silicone having anti-foam properties, 45-60% of a light liquid hydrocarbon of a specific gravity of less than 1.00, and 35-46% of a heavy liquid halogenated hydrocarbon of a specific gravity in excess of 1.00, the specific gravity of the anti-foam mix being greater than the specific gravity of the coolant formed by diluting the anti-freeze liquid with water to provide a coolant having at least 40 per cent by volume of Water so that the anti-foam mix settles in the coolant on standing.

9; A two-phase permanent type anti-freeze liquid adapted to be added to water used in cooling systems of internal combustion engines to provide a resultant substantially non-foaming coolant having a relatively low freezing point, consisting essentially of a water-miscible polyhydric alcohol freezing point depressant as the predominating constituent and forming one phase, and 0.90-1.25% by weight of an anti-foam mix to inhibit foamingof the resultant coolant during operation of the engine forming a second phase and consisting essentially, by weight 2-15% of a silicone having anti-foam properties and having about 5% of finely divided silica dispersed therein, 45-60% of a light liquid hydrocarbon of a specific gravity of less than 1.00, and 35-46% of a heavy liquid halogenated hydrocarbon of a specific gravity of more than 1.00, the specific gravity of the anti-foam mix being greater than the specific gravity of the coolant formed by diluting the anti-freeze liquid with Water to provide a coolant having at least 40 per cent by volume of water so that the anti-foam mix settles in the coolant on standing.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,007,007 Snell July 2, 1935 2,017,089 Cox Oct. 15, 1935 2,038,724 Eichengriin Apr. 28, 1936 2,071,482 Winning et al Feb. 23, 1937 2,373,570 Keller Apr. 10, 1945 2,375,007 Larson et al May 1, 1945 2,384,553 Kiffer Sept. 11, 1945 2,416,504 Trautman et al Feb. 25, 1947 2,467,177 Zimmer Apr. 12, 1949 2,524,484 Smith Oct. 3, 1950 2,528,347 Denison et al. Oct. 31, 1950 OTHER REFERENCES Dow Corning Silicon Notebook, Compound Series No. 1, copyright 1947, revised January 1949, D. C. Anti Foam A, Dow Corning Corp., Midland, Michigan. 

1. A TWO-PHASE PERMANENT TYPE ANTI-FREEZE LIQUID ADAPTED TO BE ADDED TO WATER USED IN COOLING SYSTEMS OF INTERNAL COMBUSTION ENGINES TO PROVIDE A RESULTANT COOLANT, SAID ANTI-FREEZE LIQUID CONSISTING ESSENTIALLY OF A WATER-MISCIBLE POLYHYDRIC ALCOHOL FREEZING POINT DEPRESSANT AS THE PREDOMINATING CONSTITUENT CONTAINING A SMALL AMOUNT OF CORROSION INHIBITOR DISSOLVED THEREIN AND CONSTITUTING A FIRST PHASE, AND 0.90-1.25% BY VOLUME BASED ON SAID FIRST PHASE OF AN ANTI-FOAM MIX INSOLUBLE IN SAID POLYHYDRIC ALCOHOL AND CONSTITUTING A SECOND PHASE, SAID ANTI-FOAM MIX CONSISTING ESSENTIALLY OF A FOAM INHIBITING AMOUNT UP TO 15% BY WEIGHT OF A SILICOME HAVING ANTIFOAM PROPERTIES HOMOGENEOUSLY DISPERSED IN HEAVY HYDROCARBON LIQUID HAVING A SPECIFIC GRAVITY SUCH THAT SAID ANTI-FOAM MIX HAS A SPECIFIC GRAVITY LESS THAN THAT OF THE SAID FIRST PHASE SO THAT IF FLOATS ON THE LATTER, AND GREATER THAN THAT OF THE COOLANT FORMED BY DILUTING THE ANTI-FREEZE LIQUID WITH WATER TO FORM A COOLANT CONTAINING AT LEAST 40% BY VOLUME OF WATER SO THAT THE ANTI-FOAM MIX SETTLES IN THE COOLANT ON STANDING. 